linux-kernel - Re: [PATCH] ata: ahci: power off unused ports

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Message-ID: <20080602095710.1b0de376@appleyard>
Date:	Mon, 2 Jun 2008 09:57:10 -0700
From:	Kristen Carlson Accardi <kristen.c.accardi@...el.com>
To:	Mark Lord <liml@....ca>
Cc:	Jeff Garzik <jeff@...zik.org>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Pavel Machek <pavel@....cz>, Theodore Tso <tytso@....edu>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ata: ahci: power off unused ports

On Mon, 02 Jun 2008 09:03:04 -0400
Mark Lord <liml@....ca> wrote:

> Jeff Garzik wrote:
> > Alan Cox wrote:
> >>> If you are talking about SATA -- incorrect.
> >>>
> >>> The patch deals with policy, and the user MUST have the ability to 
> >>> control this stuff.  Otherwise you create a situation where the user 
> >>> might be denied hotplug use in valid cases, or similar negative 
> >>> situations.
> >>
> >> The policy isn't however complicated. Tejun added the stuff for forcing
> >> cable type and mode on setup and has therefore written all the per device
> >> setup code we might need. Alternatively a single
> >>
> >>     foo=1/0
> >>
> >> option has been fine for acpi and will do fine for this. Total additional
> >> cost - 1 line.
> > 
> > The key requirement is per-port control.  Ideally via hdparm or another 
> > userspace tool, but kernel command line (module options) or sysfs would 
> > be just fine too.  And agreed, the minimal you need is simply 1/0 for 
> > the port's policy.
> ..
> 
> Btw.. hdparm-8.7 (unreleased) can grok /sys now, so that interface is
> as good as any from a userspace viewpoint now.
> 
> For the power-off of unused ports, the current patch still sounds
> extremely vendor-specific (Intel).

Wrong - this patch is implemented according to the AHCI spec and
has absolutely nothing vendor specific in it.

> 
> Does it actually work (demonstrate, please) on any other hardware ?

If someone would like to test it on another AHCI compliant chipset
that would be great.  I have none.
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